1. Field of the Invention
The present invention relates to over-voltage protection and particularly to a monolithic integrated circuit having such over-voltage protection means.
2. Description of the Prior Art
The normal collector to emitter breakdown voltage for NPN transistors fabricated by conventional integrated circuit technology is about 30 volts. There are occasions however in circuits employing such integrated circuits that an overvoltage fault condition arises. This may happen when a DC energy such as a battery cannot accept charging current due to a defective cell or open connection in which case the voltage applied to the integrated circuit will rise to a point which is the peak of the AC wave generated by the battery charging means, normally a 60 Hz transformer. The transformer winding may have an open circuit peak voltage approaching 50 volts.
It is desirable therefore to provide overvoltage protection means which can extend the safe operating voltage applied to an integrated circuit from about 30 to about 50 volts.
Accordingly, it is an object of the present invention to provide an over-voltage protection means for a monolithic integrated circuit.